Scale model so distance between highest and lowest vertices are equal
I would recommend using a script, see this answer https://blender.stackexchange.com/a/156501/15543

import bpy
for ob in bpy.context.selected_objects:
    if ob.dimensions.z:
        ob.dimensions *= 1 / ob.dimensions.z


will set all selected  with z dimension, to z dimension 1.

Note this is making the vertical (z direction) distance between top and bottom verts equal, and doesn't take into account x or y location at all.


  is there a way to do this without scripting?


Equiv of this per individual object in the UI